"Parabens are estrogen mimickers (agonists), with the potency of the response being related to the chemical structure (Darbre, 2008). Parabens can bind to the cellular estrogen receptor (Routledge, 1998). They also increase the expression of many genes that are usually regulated by the natural estrogen estradiol and cause human breast tumor cells (MCF-7 cells) to grow and proliferate in vitro (Byford, 2002; Pugazhendhi, 2007). Nevertheless, parabens as a class do not fully mimic estradiol as regards these changes in cellular gene expression, nor are the effects of all parabens identical (Sadler, 2009)."
I don't know much about Parabens, but I like to go as natural as possible and I personally feel estradiol is natural for me as I've lived long enough to lose the estrogen I need to feel good.
There are bonified double blind studies showing, used correctly, Vagifem and Estrace cream have absolutely minimal absorption systemically.
Each of us has to weigh the risks vs benefits of anything including baby aspirin.